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Kalcheva H.,Bulgarian Academy of Science | Terziyski D.,Institute of Fisheries and Aquaculture Plovdiv | Kalchev R.,Bulgarian Academy of Science | Dochin K.,Institute of Fisheries and Aquaculture Plovdiv | Ivanova A.,Institute of Fisheries and Aquaculture Plovdiv
Bulgarian Journal of Agricultural Science | Year: 2010

Bacterioplankton dynamics was investigated in fish ponds with carp polyculture in two-year experiment (2007- 2008, summer months). A total of seven ponds, separated in two variants of fish stocking densities with larvae of Cyprinus carpio and Aristichthys nobilis, in ratio 3:1 (Var1) and 1:3 (Var2) were studied. The total number and biomasses of bacteria ranged widely (mean cell volumes from 0.0301 to 0.1026 μm3), being twice higher in 2008 than in 2007. Most of bacteria were free-living, while those attached to detritus varied from 2 to 37%. The influence of abiotic factors, phytoplankton and zooplankton on the dynamics of bacterioplankton was revealed by different statistical analyses. Many abiotic factors (more strongly transparency and pH) influenced bacteria negatively. The greatest negative impact on number (Spearman rank correlation RS=-0.64), morphology and size groups of bacteria in spatial and temporal aspect (redundancy analysis, RDA) was caused by NO 3-N, while PO4-P influence was positive (R S=0.35, in 2008 only). Phytoplankton and bacterioplankton (mostly presented by their cell volumes) were positively related. Negative correlations (RDA) were found in 2007 between free bacteria and rotifers and between cells larger than 0.9 μm and zooplankton biomass, while in 2008 cladocerans directly reduced 2 μm-large cells and indirectly stimulated smaller and largest cells. High numbers of bacteria with various sizes, found in presence of copepods mainly in 2008 in Var1, showed their indirect positive relationships. In 2008 the two stocking variants showed significant differences (ANOVA) in morphological and size groups. Trophic cascades by carp larvae on lower levels (zooplankton and probably protozoa) resulted in high abundances of small cells (mainly cocci) in Var1, but of larger free cells and of attached to detritus bacteria and detritus particles in Var2. Our results support the findings that zooplankton grazing pressure (top-down control) negatively affects number and cell sizes, while nutrients and phytoplankton (bottom-up control) and some abiotic factors determine morphology and biomass of bacterioplankton.


Terziyski D.,Institute of Fisheries and Aquaculture Plovdiv | Kalchev R.,Bulgarian Academy of Science | Hadjinikolova L.,Institute of Fisheries and Aquaculture Plovdiv | Dochin K.,Institute of Fisheries and Aquaculture Plovdiv | Ivanova A.,Institute of Fisheries and Aquaculture Plovdiv
Bulgarian Journal of Agricultural Science | Year: 2010

The top-down effect of common carp (Cyprinus carpio L.) and bighead carp (Aristichthys nobilis Rich.) larvae with densities applied in two different proportions on several chemical variables (pH, NO 3-N, NH 4-N, PO 4-P, oxidability by KMnO 4, dissolved oxygen) in fish ponds was tested. The first two ponds were stocked with common carp and bighead carp larvae in abundance proportion 3:1 (variant 1), while further two ponds were stocked in 1:3 ratio of the same fish species (variant 2). The experiment lasted 4 months (May to September) and was repeated in two consecutive years (2007, 2008). The first year experiment was carried out on ponds from two different localities (with two different water sources: surface and underground) equally presented in each stocking variant, while second year experiment took place in one and the same locality but variant No2 was carried out on three instead on two ponds. The first year experiment showed a single statistically significant difference between two stocking variants for oxidability, while the second year experiment revealed significant differences for both multiple comparison of recorded chemical variables and for two single comparisons (pH and dissolved oxygen) in favor of variant No2. However, the underground water proved to be richer in NO 3-N, showed higher N P -1 ratio and pH after entering the ponds. In the first year multiple seasonal variations of chemical variables were related to physical while in the second year to biological variables.


Terziyski D.,Institute of Fisheries and Aquaculture Plovdiv | Kalchev R.,Bulgarian Academy of Science | Dochin K.,Institute of Fisheries and Aquaculture Plovdiv | Piskov I.,Institute of Fisheries and Aquaculture Plovdiv | And 2 more authors.
Bulgarian Journal of Agricultural Science | Year: 2010

The top-down effect of densities of common carp (Cyprinus carpio L.) and bighead carp (Aristichthys nobilis Rich.) larvae applied in proportions 3:1 and 1:3 on biological fish pond characteristics like plankton primary production, respiration, abundances of bacterio, phyto and zooplankton, chlorophyll etc. was tested. The experiment lasted 4 months (May to September), was repeated in two consecutive years (2007, 2008) included four ponds in year 2007 from two different localities and five ponds in 2008 from one and the same locality. The measured biological variables showed statistically significant differences between means of localities, years and stocking variants. The sources of variations between localities and years have their ground in objective circumstances accompanying the experiment implementation but could not override the top-down effect of fish stocking variants. The variant 1 (3:1 common carp: bighead carp densities) which proved to be more effective was distinguished by higher phytoplankton and lower zooplankton abundances. Its primary production and respiration were also lower than in variant 2 (1:3 densities of common carp: bighead carp).


Iliev I.,Plovdiv University | Kostadinova S.,Plovdiv University | Marhova M.,Plovdiv University | Hubenova T.,Institute of Fisheries and Aquaculture Plovdiv | Zaikov A.,Institute of Fisheries and Aquaculture Plovdiv
Bulgarian Journal of Agricultural Science | Year: 2015

The aim of this study was to determine the total count of main microbial indicators for the water quality of Dospat Dam Lake. Samples were taken from six stations situated in the aquatory of the reservoir and one station at Dospatska River. The seasonal dynamics of the total viable count (TVC 20°C), total coliforms (TC), E. coli, fecal streptococci (FS) and C. perfringens were studied for the period April 2011-March 2012. The values for the TVC 20oC were within range of 1.103cfu.100 mL-1 to 39.103 cfu.100 mL-1, without statistically significant differences between stations (ANOVA, P > 0.05). The average values for TC varied from 10 cfu.100 mL-1 to 100 cfu.100 mL-1 and in August it rose to 1000 cfu.100 mL-1 with higher numbers near the net cage farms (ANOVA, P < 0.005). Presence of E. coli, FS and C. perfringens during the spring months was not established. Slight increase of the sanitary-state indicator was observed in August with values of 26 cfu.100 mL-1, 20 cfu.100 mL-1 and 10cfu.100 mL-1 for E. coli, FS and C. perfringens respectively, with similar trends in November. Coliforms were characterized by low species diversity with domination of Serratia marcescens, Pantoea aglomerans, Hafnia alvei and Entero-bacter cloacae at stations tree, four and five. The highest number of species was observed at station six (near Sarnitza village). © 2015, National Centre for Agrarian Sciences. All rights reserved.


Hubenova T.,Institute of Fisheries and Aquaculture Plovdiv | Zaikov A.,Institute of Fisheries and Aquaculture Plovdiv | Katsarov E.,Institute of Fisheries and Aquaculture Plovdiv | Terziyski D.,Institute of Fisheries and Aquaculture Plovdiv
Bulgarian Journal of Agricultural Science | Year: 2015

The aim of the experiment was to test two methods of juvenile pikeperch weaning from live food to artificial diet: variant 1: 8 days co-feeding with dry feed and frozen chironomids, followed by dry feed feeding and variant 2: two days feeding with frozen chironomids, followed by dry feed feeding. 1560 individuals of juvenile pikeperch with mean initial total length (TL) 2.540 ± 0.04 cm, weight (W) 0.181 ± 0.01 g and condition factor (K) 1.107 ± 0.03 from a earth pond were randomly distributed into 4 plastic tanks in a flow water system. The study was performed at stocking density of 6 ind.l-1 in double repeat. The weaning success was evaluated after 20 day rearing period. In the variant 1 there was achieved significantly higher survival rate (mean 52.95%) in comparison with the variant 2 (mean 26.80%). The values of specific growth rate, body weight and body length are better in variant 1 than in variant 2, respectively: 2.184%/0.502%; 0.487 ± 0.02 g/0.377 ± 0.02 g; 3.711 ± 0.07 cm/3.356 ± 0.05 cm. © 2015, National Centre for Agrarian Sciences. All rights reserved.

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